Go to homepageCyberStrike

Menu

Star on GitHub · 3.2k
Sign inDownload

CVE-2026-56390

6.3 · MEDIUM

GNU Bison improperly handles grammar‑defined output paths.

Published Jul 29, 2026CWE-73EPSS 0.18%

Overview

CVE-2026-56390 is a medium-severity vulnerability. It was published on July 29, 2026 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

Technical description

GNU Bison improperly handles grammar‑defined output paths. Grammar directives such as %output and %header allow specifying file paths, which are accepted without restriction and override caller‑supplied output options.

When processing attacker-supplied grammar, this behavior allows directing generated files to arbitrary writable locations on the filesystem, potentially overwriting existing files accessible to the Bison process.

Maintainers of this project were notified about this vulnerability, and fixed the issue in commit 8d101c19d4d9aaedf83a448c925513742d4efcf0. However, they did not provide vulnerable version range. Version 3.8.2 was tested and confirmed as vulnerable, other versions were not tested but might also be vulnerable.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

Refcert.pl/en/posts/2026/07/CVE-2026-56389Refcgit.git.savannah.gnu.org/cgit/bison.git/Refcgit.git.savannah.gnu.org/cgit/bison.git/commit/?id=8d101c19d4d9aaedf83a448c925513742d4efcf0

How CyberStrike helps

Frequently asked questions

What is CVE-2026-56390?

CVE-2026-56390 is a medium-severity vulnerability. It was published on July 29, 2026 and has a CVSS 3.1 base score of 6.3 (MEDIUM).

How severe is CVE-2026-56390?

This vulnerability has a CVSS 3.1 base score of 6.3, rated MEDIUM. It requires local or adjacent network access to exploit. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-56390?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-56390?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-56390 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

Related MEDIUM CVEs from 2026

View all
Browse by year2026202520242023202220212020201920182017201620152014201320122011201020092008200720062005200420032002200120001999